When Multiprotocol Label Switching (MPLS) is implemented in transport networks (such as MPLS-Transport Profile (MPLS-TP)), it is essential that transport network properties are preserved in the packet domain. Specifically, the uniqueness and integrity of an individual point-to-point connection must be maintained from end-to-end, to allow monitoring integrity and performance with dedicated data path Operations, Administration, and Maintenance (OAM), uncontaminated by information from any other path. This end-to-end path integrity is not maintained by native MPLS; typically paths from different sources to a common destination are merged, to enhance scalability. There is no intrinsic mechanism in MPLS-TP to prevent such merging of paths, it is merely a convention of the MPLS-TP control entity that separation of paths is preserved.
Also, there is an evolving technique known as Header Space Analysis (HSA), which uses an algebra of packet headers propagated through a network model, to probe destinations reachable from sources in a general way, rather than relying on specific use-cases to sample reachability. As a consequence, it offers an analytic technique to prove the validity of its results. A key aspect of the HSA technique is its computability; because a whole volume of header space can be encoded in one header value, it allows exhaustive testing of networks of significant scale, which would be out of reach of investigations by brute-force application of binary-coded headers. Currently published applications of HSA are reachability analysis, loop detection, and Virtual Private Network (VPN) (“slice”) isolation.
The transport application introduced above has not been disclosed in the HSA. Although “VPN isolation” has a related objective, the separators in that application use a simple domain-wide Virtual Local Area Network (VLAN) or other VPN Identifier (e.g. as defined in RFC 4364) to achieve isolation, not a coordinated hop-by-hop selection from a single flat label space, as in the transport application.